Influence of vitamin D on fecal shedding of Escherichia coli O157:H7 in naturally colonized cattle.

Three experiments were conducted to evaluate the influence of vitamin D on fecal shedding of Escherichia coli O157:H7 in cattle. In the first experiment, two groups of cattle (beef and dairy) were assigned to a control treatment or to receive 0.5 × 10(6) IU vitamin D per day via oral bolus for 10 days. Fecal samples were collected before and throughout the dosing period for culture of E. coli O157:H7. No differences were observed for fecal shedding of E. coli O157:H7 among treatments for either beef or dairy animals. Serum concentrations of vitamin D were markedly higher (P < 0.0001) in treated beef cattle but only tended to be higher (P = 0.09) in the dairy cattle. In the second experiment, three successive vitamin D dosages (2,400, 4,800, and 9,600 IU/day; 14 days each) were administered to 14 dairy steers (7 steers served as controls), fecal samples were collected daily, and serum samples were collected weekly throughout the 42-day experimental period. No significant differences in fecal prevalence or serum vitamin D concentrations were observed for any of the vitamin D dosages. A third experiment sampled feedlot cattle (winter and summer) to determine whether serum vitamin D concentrations were correlated with fecal shedding of E. coli O157:H7. A fecal sample and a blood sample were obtained in each season from 60 randomly selected animals (total of 120 fecal samples and 120 corresponding blood samples). As expected, season was highly correlated (r = 0.66) with serum vitamin D concentration with higher concentrations (P < 0.01) observed in the summer. E. coli O157:H7 prevalence (percentage of positive samples) was not highly correlated (r = 0.16) with season, although the correlation tended to be significant (P = 0.08). The proportion of cattle shedding E. coli O157:H7 was 16.7 and 6.7% for the summer and winter collections, respectively. Results of this research do not support a correlation between vitamin D intake and E. coli O157:H7 shedding in cattle.